1. Field of Invention
The present invention relates to a diode structure and a manufacturing method thereof, and particularly to a light emitting diode (LED) structure and a manufacturing method thereof.
2. Description of the Related Art
Over the years, LED devices with a cluster of varied GaN (gallium nitride) compounds, such as GaN (gallium nitride), AlGaN (aluminum gallium nitride), InGaN (indium gallium nitride), have caught much attention in semiconductor industry. The above-mentioned group III A nitride belong to a wide-bandgap semiconductor material family, whose light-wavelengths range from ultraviolet to red light, almost covering the entire visual light waveband. Compared with the conventional light bulbs, LEDs have overwhelming advantage, such as small size, longer lifespan, low driving voltage/current, break-resistance, no mercury (no pollution) and good luminous efficiency (low electricity consumption). With these advantages, LEDs are widely applied in the industry.
FIG. 1 is a schematic cross-sectional view of a conventional LED. Referring to FIG. 1, a conventional LED 100 includes an aluminum-oxide substrate 110, a doped semiconductor layer 122, a light-emitting layer 124 and a doped semiconductor layer 126. Wherein, the doped semiconductor layer 122 is disposed on the aluminum-oxide substrate 110, while the light-emitting layer 124 is located on a partial area of the doped semiconductor layer 122, and the doped semiconductor layer 126 is disposed on the light-emitting layer 124. Note that the above-mentioned doped semiconductor layer 122 and the doped semiconductor layer 126 are different types of doped semiconductors. For example, if the doped semiconductor layer 122 is a P-type doped semiconductor, the doped semiconductor layer 126 must be an N-type doped semiconductor.
In more detail, on the doped semiconductor layer 126 and the portion of the doped semiconductor layer 122 uncovered by the doped semiconductor layer 126, a bonding pad 132 and a bonding pad 134 are usually disposed, respectively. The bonding pads 132 and 134 are made of metal. According to the prior art, a conventional LED is electrically connected to a circuit board or other carriers in a wire-bonding technology or flip-chip bonding technology, wherein the bonding pads 132 and 134 serve as a medium for connecting the LED 100 to the circuit board or other carrier. Besides, there is another conventional LED, which is described in the following with reference to FIG. 2.
FIG. 2 is another schematic cross-sectional view of a conventional LED. Referring to FIG. 2, a conventional LED 200 includes a conductive substrate 210, a doped semiconductor layer 222, a light-emitting layer 224 and a doped semiconductor layer 226. Wherein, the doped semiconductor layer 222 is disposed on the substrate 210, while the light-emitting layer 224 is disposed between the doped semiconductor layer 222 and the doped semiconductor layer 226.
Similarly, a bonding pad 232 is usually disposed on the doped semiconductor layer 226 and the bonding pad 232 serves as the same function as the bonding pad 132. However, the conductive substrate 210 is conductive. Therefore, when the conventional LED 200 is disposed on a circuit board or other carriers, the circuit board 210 can be electrically connected to the circuit board directly through the conductive wires disposed on the bonding pad 232 (not shown in the figure).
In the above-described two conventional LEDs, the internal temperature thereof would gradually rise as the time of luminescence increases, then gradually bringing down the luminous efficiency. Furthermore, a crowding effect would take place near the bonding pad when driven, which might damage the bonding pad or the adjacent semiconductor layer, bringing a halt to the LED normal operation.